Electric-discharge device



Nov. 8, 1927.

1,648,293 E. E. CHARLTON ELECTRIC DISCHARGE DEVICE Original Filed Nov. 29. 1922 Inventor: Ernest Bcharltoh,

His Attorney.

Patented Nov. 8, 1927.

UNITED STATES 1,648,293- P'AT'ENT OFFICE.

ERNEST E. CHARLTON, OF'SCH ENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELEC- TRIO COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC-DISCHARGE DEVICE.

Application filed November 29, 1922, Serial No. 604,088. Renewed September 23, 1927.

The present invention relates to devices containing an ionizable gas, as for example. argon,in which an electric discharge is produced between electrodes one of which preferably operates at incandescence. It is the object of my invention to improve the efficiency and operating characteristics of these devices.

In the manufacture of gas-filled electric discharge devices it has been found desirable to provide'a chemical reagent, as for example, metallic calcium or magnesium,

which is capable ofcombiningwith watervapor, and other deleterious gases, which are unavoidably present as impurities in the gaseous filling or are given off by parts of the device during operation.- Whatever may be the action of these chemical additions, their effect is to lower the fall of potential in these. devices, thus increasing their ef- I have discovered that the alkali metal caesium when present in appreciable amounts in thermionic devices containing a' gas, not only lowers the voltage drop to a materially lower value than heretofore obtainable with alkaline reagents such as magnesium, but that in addition the .current value obtainable with a given voltage is materially increased. The accompanying drawing shows a rectifier as an example of anincandescent cathode gas-filled device provided with a quantity of alkali metal.

The device illustrated comprises. an envelope ,1, consisting of suitable refractory glass, a cathode 2 consisting of tungsten, or

other suitable highly refractory metal, and an anode 3' consisting of graphite, tungsten, or other suitable conductive material. The cathode is. shown as constituted by a heavy, coiled filament connected to leading-in conductors 4, 5, sealed as usual into a stem 6, and contacting with a screw base 7, whereby a heating. current may be conveyed to heat of argon, neon, hydrogen, helium or other tenth or a few tenths of one per cent of the total pressure in the-bulb. 1 c

The bulb preferably is given a preliminary exhaust by the methods used in exhausting incandescent lamps. Argon or other suitable gas at a pressure of several millimeters to several centimeters then is introduced and a discharge is operated in the bulb to drive gas out of the. anode. This preliminary gas filling is pumped out, the desired quantity of alkali metal is introduced, and another gaseous filling at the desired pressure is admitted. The .exhaust and gas-admitting conriection isindicated as sealed off byfusion at 1 While the desired quantity of caesium may be introduced in-any. convenient way, I prefer to introduce the same from a reaction mixture comprising a reducible compound of the desired metal and a reducing material. For example, caesium may be supplied'from a side tube 12 containing as a'preferable source, a mixture of caesium chloride and an excess of finely divided magnesium- A reaction brought about by heating-the tube 12 evolves caesium. The'rcduced metal first accumulates .in the bulbs 13 and from thence is conveyed by the connecting tube .14 into.

themain container. Enough alkalimetal is introduced to-provide an excess over the amount required to combine with water vapor, or other deleterious gases. The tube 12 may remain attached to the main contamer. during the operation of the device, or

may be sealed off by fusion, as indicated by,

dotted lines, within the tube 14. At ordinary operating temperature the pressure of the alkali metal is of the order of magnitude of a micron.

In some cases, the reaction mixture may be applied to a convenient interior part of the device, as for example, to sdme part lot the cathode or anode, thus dispensing with a side chamber. The alkali metal then is evolved by is applied. 7

These methods; of introducing a desired the reaction resulting when heat.

llO'

alkali metal into an electrical discharge device are described and claimed by me in a co-pending application Serial No. 608,311

filed December 21, 1922.

"- of argon at a pressure of about 5 cm. of

mercury, a direct current output of about five amperes is obtained with a voltage drop of about 8.3 volts, this value being materially below the ionization voltage of argon which is about 15 volts. The addition of caesium in this device increases the direct current output underthe same conditions to 7.5 amperes and decreases the voltage drop to 5.7 volts, no ageing being required.

Rubidium maybe used in place of caesium,

hence whenever in the appended claims I have specified caesium, I wish also to include" rubidium as an equivalent.

WVhat I claim as new and desire to secure by Letters Patent of the United States, is 1. An electric discharge device comprising a container, a refractory cathode, an anode, a gaseous filling therein at a substantial pressure sufiicientlyhigh to permit operation of I 'a thermionic discharge with a voltage between said electrodes below the ionization voltage of said gas and a suflicient quantity of alkali'metal having an atomic weight greater than that of potassium in said container to reduce the operation voltage to a value lower than the value characteristic of the gaseous filling under the given conditions.

2. An electric rectifier comprising a container, a thermionic cathode, an anode adapted to operate at a substantially lower temperature than said cathode, a gas filling at a pressure of the order of magnitude of several centimeters of mercury, and a quantity of alkali metal having an atomic weight greater thanthat of potassium in said container, said device being constructed to operate at a temperature at which caesium has a vapor pressure of the order of about one micron of mercury.

3. An electric rectifier comprising a container, a thermionic cathode, an anode of solid conducting material, an atmosphere of argon of about five cm. of mercury pressure and a quantity of caesium sutficient to increase the current-carrying capacity and cause the voltage drop in said rectifier, to be about five volts with a thermonic current of about seven amperes. Y

In witness whereof, I have hereunto set my hand this 27th day of November, 1922.

ERNEST E. CHARLTON. 

